The purpose of this study is two-fold: 1) To investigate the pharmacokinetics and pharmacodynamics of methadone in methadone maintained mothers and their newborn infants, 2) To follow the growth, neurological and behavioral development of these infants through the first three years of life. Methadone pharmacokinetics will be studied to elucidate the differences in its metabolism and excretion in the pregnant and nonpregnant methadone-maintained women. We would further investigate 1) the individual differences in metabolism of methadone in these newborn infants and 2) the neonatal as well as the maternal methadone metabolism relationship to neonatal withdrawal syndrome. Because of the very few studies available and the conflicting observations on infants born to methadone maintained mothers, these infants will be followed for their first 3 years of life at frequent designated intervals in order to systematically evaluate methadone effect. Thus we hope to be able to define any beneficial or detrimental effects methadone may have on the child born to a methadone maintained mother compared to a similar drug free control group. The patient population will consist of methadone maintained mothers who are registered in our High Risk Perinatal Obstetrical Clinic. We also include those mothers who arrive directly at our labor-delivery suite.